"Charles Ellson" wrote in message
...
On Mon, 12 Mar 2012 11:08:51 -0700, "Roger Traviss"
wrote:

If you have an out of country phone in either Canada or the
United
States, the roaming costs to go to the other country are
noticeable....

Here in Victoria, if you are down by the waterfront, you may
get hit by
roaming changes for even a local call.

Why? Because your call gets picked up by a cell tower in
Blaine, Washington
State. :-)

That has been alleged to have happened on English south coast
shores/beaches which are screened from the local transmitter by
high
cliffs but within range of French base stations.

Sometimes, exceptional atmospheric conditions can cause this from
elevated inland points as well.

I was at the Great Dorset Steam Fair http://www.gdsf.co.uk at
Tarrant Hinton, and made some calls to friends who were elsewhere
on the very large fair site. When I got the bill, I discovered I
had apparently made calls in France *and* the UK within a few
seconds of each other.

The mobile phone systems utilise a transmission protocol known as
TDMA (Time Division Multiple Access). In theory, this should
block connections where the propogation delay is more than 28
milliseconds (equating to a distance of about 90km). In my case,
the nearest point of the French coast was at least 130km away -
so it shouldn't have been possible, but it definitely happened. I
seem to remember I got the roaming charge refunded.

--
MatSav